Abstract
Top‐down population regulation can influence the success of biological control agents when they are released into the field. Entomopathogenic nematodes ( EPN s) are used commonly in biological control programmes, but their efficacy suffers from poor persistence. Although abiotic soil conditions have been shown to reduce EPN persistence, consumption of infected insects by scavengers and of infective juvenile ( IJ ) nematodes by predators may also regulate these populations. In the present study, the effects of different soil arthropods on EPN s in laboratory conditions were measured. It was hypothesised that arthropods commonly found in soil communities where EPN s are applied would consume cadavers of insects parasitised by the nematodes and the IJ s themselves. Some species of scavengers consume EPN ‐infected insects. Crickets ( Gryllus bimaculatus De Geer), A merican cockroaches [ Periplaneta Americana (Linnaeus)], ants [ Tetramorium chefketi Forel and Pheidole pallidula (Nylander)], earwigs ( Labidura riparia Pallas), mites ( Sancassania polyphyllae Zachvatkin), and springtails ( Sinella curviseta Brook and Folsomia candida Willem) have different responses to nematode‐killed insects. Results suggested that ants ( T. chefketi ), cockroaches, mites, and earwigs fed on Steinernema ‐killed insects whereas neither crickets nor springtails consumed them. In the second part of the study, experiments were conducted to determine whether mites and springtails consumed IJ EPN s. Results showed that S. polyphyllae mites do not consume infective juveniles in soil, whereas both springtail species consumed significant numbers of the IJ s. Top‐down regulatory processes can be a limiting factor for EPN populations under laboratory conditions. Both host cadavers and IJ s are consumed (albeit by different arthropods), so these results may help explain the difficulties associated with the persistence of EPN application to soil.